1. Field of the Invention
The present invention relates to a synchronous reluctance motor (SynRM), and more particularly, to a speed control apparatus of a synchronous reluctance motor.
2. Description of the Background Art
FIG. 1 is a sectional view of a general synchronous reluctance motor (SynRM), in which reference numeral 100 denotes a stator, 101 denotes slots of the stator 100, and 200 denotes a rotor.
FIG. 2 is a sectional view of the rotor of FIG. 1, in which reference numeral 201 denotes grooves which differentiate magnetic flux passing xe2x80x98dxe2x80x99 axis and xe2x80x98qxe2x80x99 axis, 202 denotes a pinhole with silicon ferrite filled therein.
A rotational speed of the synchronous reluctance motor with such a structure is controlled by a synchronous reluctance motor controlling apparatus which detects a position of the rotor.
FIG. 3 shows the construction of the speed controlling apparatus of the synchronous reluctance motor in accordance with a conventional art.
As shown in FIG. 3, a rectifier 320 receiving an AC power 310 and rectifying it to a DC power, an inverter 330 for converting the DC power to three phase currents and driving the synchronous reluctance motor 340, a controlling unit 350 controlling the inverter 330, and a detecting unit 360 detecting a rotational speed or the synchronous reluctance motor 340.
The detecting unit 360 includes a current detector 361 detecting two phase currents among the three phase currents flowing to the synchronous reluctance motor 340, a rotor position detector 363 detecting angular velocity of the rotor of the synchronous reluctance motor 340, a magnetic flux angle operating unit 362 receiving the angular velocity (xcfx89r) of the rotor outputted from the rotor position detector 363 and computing a magnetic flux angle (xcex8), and a coordinate converter 364 receiving magnetic flux angle (xcex8) and the detected two phase currents and generating a magnetic flux current value (ids) of the rotor and a current value iqs of torque.
The controlling unit 350 includes a comparator 358 receiving the angular velocity value (xcfx89r) and a velocity command value (xcfx89r*) from the rotor position detector 363 and computing a difference velocity command value, a speed controller 356 receiving the different velocity command value and generating a current command value for torque (lqs*), a comparator 354 receiving the current command value for torque (lqs*) and a current value for torque (iqs) outputted from the coordinate converter 364 of the detecting unit 360 and generating a difference current command value for torque, a magnetic flux command generator 357 generating a current command value for magnetic flux (ids*) to differentiate a positive torque region and a positive output region according to the rotor angular velocity value (xcfx89r) outputted from the rotor position detector 363 of the detecting unit 360, a comparator 355 receiving the current command value (ids*) and the current value for magnetic flux (ids) outputted from the coordinate converter 364 of the detecting unit 360 and generating a difference current command value for magnetic flux, a magnetic flux controller 353 receiving the difference current command value for magnetic flux and generating a magnetic flux command value; a current controller 352 receiving the command value for magnetic flux and the difference current command value for torque and generating a voltage command value for torque (Vqs*) and a voltage command value for magnetic flux (Vds*), and a voltage generator 351 receiving the voltage command value for torque (Vqs*), the voltage command value for magnetic flux (Vds*) and the magnetic flux angle (xcex8), generating three phases voltage command values (Vas, Vbs, Vcs) and outputting them to the inverter 330.
The operation of the conventional speed control apparatus of synchronous reluctance motor constructed as described above will now be explained.
In order to control the rotation speed of the synchronous reluctance motor 340 according to the velocity command value (xcfx89r*), when the velocity command value (xcfx89r*) is inputted to the controller 350, the comparator 358 of the controlling unit 350 compares the velocity command value (xcfx89r*) and a rotor angular velocity value (xcfx89r) outputted from the rotor position detector 363 and outputs a generated error to the speed controller 356.
Then, the comparator 355 of the controlling unit 350 receives the angular velocity value (xcfx89r), receives the current command value for magnetic flux (ids*) generated from the magnetic flux command generator 357 and the current value for magnetic flux (ids) outputted from the coordinate converter 364, compares them to generate a difference current command value for magnetic flux and outputs it to the magnetic flux controller 353.
The current controller 352 receives the difference current command value for torque and the magnetic flux command value outputted from the magnetic flux controller 353, generates a voltage command value for torque (Vqs*) and a voltage command value (Vds*) for magnetic flux and outputs them to the voltage generator 351.
Then, the voltage generator 351 receives the voltage command value for torque (Vqs*), the voltage command value for magnetic flux (Vds*) and the magnetic flux (xcex8) outputted form the magnetic flux angle operating unit 362 of the detecting unit 360, and outputs three phase voltage command values (Vas, Vbs, Vcs) for switching ON/OFF of the inverter 330 to the inverter 330.
Thus, the synchronous reluctance motor 340 is rotated by the three phase AC powers outputted from the inverter 330.
The coordinate converter 364 of the detecting unit 360 converts an a-phase current (las) and a b-phase current (ibs) detected from the current detector 361 which detects a current flowing from the inverter 330 to the synchronous reluctance motor 340 into a d-axis current or a current value for magnetic flux (ids) and a q-axis current or a current value for torque (iqs).
The rotor position detector 363 uses an encoder or a hall sensor to detect a position of the rotor.
The conventional speed control apparatus of the synchronous reluctance motor, however, has the following problems.
That is, in order to control the rotation speed of the synchronous reluctance motor, an encoder or the hall sensor is to be used to detect a position of the rotor of the synchronous reluctance motor, which causes an increase of a cost of a product. Above all, the rotor position detector is not suitable to a compressor of a refrigerator, an air-conditioner or a heater.
Therefore, an object of the present invention is to provide a speed control apparatus of a synchronous reluctance motor that is capable of controlling a rotation speed of a synchronous reluctance motor.
Another object of the present invention is to provide a speed control apparatus that is capable of controlling a rotation speed of a synchronous reluctance motor by detecting a current and a voltage supplied to a synchronous reluctance motor.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided to a speed control apparatus of a synchronous reluctance motor including: a rectifier for receiving an AC power and rectifying it to a DC power; an inverter for receiving a DC power to an AC power and supplying it to a synchronous reluctance motor; a detecting unit for operating an induction voltage generated by detecting a current and a voltage supplied to the synchronous reluctance motor and the estimated induction voltage generated from the current, and generating an estimated angular velocity of the synchronous reluctance motor; and a controller for receiving the estimated angular velocity and the velocity command value inputted by a user and controlling the speed of the synchronous reluctance motor through the inverter.
To achieve the above object, there is also provided a speed control method of a synchronous reluctance motor including the steps of: detecting a current supplied to a synchronous reluctance motor; detecting a voltage supplied to the synchronous reluctance motor; operating an induction voltage generated by operating the detected current and an estimated induction voltage generated from the current, and generating an estimated angular velocity of the synchronous reluctance motor; and controlling the speed of the synchronous reluctance motor according to the estimated angular velocity and a velocity command value inputted by a user.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.